1. Field of the Invention
This invention relates to a device attached to a vehicle wheel hub for recording the distance covered by the vehicle and comprising a counting mechanism, a printing mechanism for stamp cards and feed means for feeding the counting mechanism wheels as a function of said distance. Such a device is disclosed in copending U.S. patent application Ser. No. 549,702, filed Feb. 13, 1975, incorporated herein by reference and now abandoned.
2. Technical Considerations and Prior Art
The distance measuring instrument in question can be coupled and attached to wheel hubs of both traction vehicles and trailers coupled to such vehicles. In view of the fact that the distance measuring instrument is intended to be attached to a wheel hub, it may be called "hub meter". Its counting mechanism may be of any conventional design comprising number wheels provided with types or printing dyes. The hub meter further comprises a mechanism with stationary number types corresponding to the apparatus number of the meter. The stamping mechanism may be of known design and is intended to release the printing of the values of the number types in question on the number wheels in the counting mechanism, i.e., the distance in kilometers covered by the vehicle, onto a stamp card, which for this purpose is introduced into the hub meter. At the same time, said apparatus number is printed. The stamp card, which is provided with carbon paper, is introduced for printing through a card slot in the meter, which slot becomes accessible when a covering or protective lid on the free end of the meter is pivoted or folded aside. Said lid, in addition to sealing the meter to prevent dirt from entering thereinto, also acts as a handle for releasing the printing mechanism. When the lid is to be folded aside, a screw in the lid is actuated to release the lid from the apparatus casing, whereafter the lid is actuated for exposing the slot to introduce the stamp card therethrough. The lid is then, for printing, actuated in a definite way in order to release the printing mechanism to print on the stamp card introduced into the card slot. The movement of the lid in this conjunction may be a rotary or a folding movement.
The hub meter, further, may comprise a curtain or slide, which normally shuts the card slot, but is opened when the meter is being operated for card printing, and thereafter is shut to prevent improper objects, which may block the counting mechanism, from being introduced into the meter through the card slot. Such curtains have been proposed previously for meters of other types.
The hub meter may in addition include a base plate, which is intended for mounting and supporting the meter and faces towards the wheel hub, to which it is attached. Said base plate is heat-insulated from the remaining details of the meter, so that heat produced by the vehicle wheel cannot be transferred by conduction to the interior of the meter.
The number wheels of the counting mechanism may be arranged to be advanced by jumps, irrespective of the rotational direction of the vehicle wheel.
It is understood that a hub meter rotates together with the vehicle wheel to which the meter is attached when the vehicle is driven. The counting mechanism rigidly mounted in the meter housing then also rotates together with said wheel. For rendering it possible for the counting mechanism wheels to be advanced in synchronism with the movement of the vehicle wheel and meter, a feed mechanism actuated by the rotation of the meter must be introduced. For this purpose, a non-rotary reference means must be introduced into the meter as a fixed "reference point". According to the invention, a pendulum mechanism is utilized which, by action of gravitation, maintains a substantially constant position, independently of the rotation of the meter and counting mechanism, and which actuates the feed mechanism for the number wheels of the counting mechanism. Said pendulum mechanism comprises a pendulum with a swing axle, which is concentric with the vehicle axle, and includes means for coupling said axle to the feed mechanism.
Under such operational conditions as acceleration and retardation of a vehicle, when the vehicle drives down into holes in the road, etc., a pendulum tends to turn round one or more revolutions, and at its worst has the tendency of participating in the rotary movement of the hub meter, which is attached to and caused to rotate by said wheel, so that the feed mechanism of the counting mechanism remains unaffected and, consequently, recording of the covered distance does not take place. The pendulum according to the invention is so designed that such inconveniences due to incorrect recording of covered distances are avoided. The pendulum, more precisely, has been given the shape of a thin-walled, hollow ring with smooth inner surface. The annular space in the ring is filled to some part with movable spherical balls of a heavy material, for example lead. The balls can move freely relative to each other and to the inner walls of the ring. The resulting friction effect implies an effect consumption, which efficiently brakes the ring under such conditions, which otherwise would have caused a pendulum with lumped mass to participate in the rotation of the meter. The pendulum, furthermore, is provided with a fixed balance weight, in order to prevent the annular pendulum from slowly migrating around when it is subjected to vibration forces. Owing to the gravity force, the unbalance thus obtained in the pendulum system with ring and balls will cause the pendulum to assume a substantially constant static position.